Epoxy polymeric nonolinear optical materials based on glycidyl amines

ABSTRACT

The present invention is directed to an epoxy-containing polymeric material having nonlinear optical properties, particularly a glycidyl amine polymer, and a process for making the nonlinear optical (NLO) epoxy-containing polymeric material including poling the polymeric material under high voltage at elevated temperature for a period of time to bring about orientation of the nonlinear optical functionalities in the polymer. The polymers have enhanced thermal stability and good NLO properties.

FIELD OF THE INVENTION

The present invention relates to polymeric organic materials whichpossess nonlinear optical (NLO) properties, and more particularly, thepresent invention relates to epoxy-containing polymeric nonlinearoptical materials which are useful in nonlinear optical devices, and aprocess for preparing the NLO materials.

BACKGROUND OF THE INVENTION

Information is more rapidly processed and transmitted using optical asopposed to electrical signals. There exists a need for finding nonlinearoptical materials, and processes for preparing such materials, whichalter the transmission of optical signals or serve to couple opticaldevices to electrical devices, i.e., electrooptic devices.

Some materials which have been used in electrooptic devices includesemiconductors such as lithium niobate, potassium titanyl phosphate andgallium arsenide and most recently, organic materials which have beendoped with nonlinear optical materials. Generally, polymeric organicmaterials can or may have the specific advantages of fast response time,small dielectric constant, good linear optical properties, largenonlinear optical susceptibilities, high damage threshold, engineeringcapabilities, and ease of fabrication.

There are various known polymeric organic materials which possessspecific nonlinear optical properties and various known processes formaking such polymeric organic materials. Many of the current polymericorganic materials prepared by the prior art are prepared by blending aNLO molecule into a polymer host material. "Blending" herein means acombination or mixture of materials without significant reaction betweenspecific components.

Nonlinear optical properties of organic and polymeric materials was thesubject of a symposium sponsored by the ACS division of PolymerChemistry at the 18th meeting of the American Chemical Society,September 1982. Papers presented at the meeting are published in ACSSymposium Series 233, American Chemical Society, Washington, D.C. 183.The above-recited publications are incorporated herein by reference.

EF 218,938 discloses one method of making a polymer with nonlinearoptical properties by incorporating molecules which have nonlinearoptical (NLO) properties into a host polymer. The NLO molecules areincorporated into the host polymer by blending. The NLO molecules in thepolymer can be aligned by an electric field while the temperature of thepolymeric material is raised above its glass transition temperature andthen cooled to room temperature. EP 218,938 discloses a number ofpolymer host materials, including epoxies, and many types of moleculeswhich have NLO activity including azo dyes such as disperse red 1.

PCT Application WO8802131A also describes a method of blending asubstance having nonlinear optical properties, such as2-methyl-4-nitroaniline, into a commercially available curable epoxyresin polymer to prepare an electrooptical material.

It is also known to incorporate a NLO active group such as azo dyeDisperse Red 1 (4,[-N-ethyl-N-(2-hydroxyethyl] amino-4-nitroazobenzene), by simply blending the azo dye in a thermoplastic materialsuch as poly(methylmethacrylate), as described in Applied PhysicsLetters 49(5), 4 (1986). In this paper, an aromatic amine is disclosedbut the amine is not covalently bonded to the polymer chain. Inaddition, the paper discloses an NLO molecule which has an electrondonor and acceptor group at either end of the molecule.

A problem associated with a polymer with NLO properties produced bysimply blending NLO molecules into a host polymer is that these polymermaterials lack stability of orientation, i.e., there is a great amountof molecular relaxation or reorientation within a short period of timeresulting in a loss of NLO properties. For example, as reported byHampsch et al., Macromolecules 1988, 21, 528-530, the NLO activity of apolymer with NLO molecules blended therein decreases dramatically over aperiod of days.

Generally, the incorporation of molecular structures which have NLOactivity into the backbone of a polymer chain will decrease thelikelihood of the structural reorganization in comparison with polymersin which the NLO active molecule is simply blended. It is thereforedesirable to provide a polymer material with NLO groups covalentlybonded to the backbone of the polymer material to minimize relaxationeffects.

U.S. Pat. No. 4,703,096 discloses a polymer composition in which the NLOactivity is derived from aromatic structures attached to a polymericdiacetylenic backbone. However, the synthesis of the material describedin U.S. Pat. No. 4,703,096 is complicated.

There is a continuing effort to develop new nonlinear optical polymerswith increased nonlinear optical susceptibilities and enhanced stabilityof nonlinear optical effects. It would be highly desirable to haveorganic polymeric materials, particularly polymeric materials based onepoxy resins, with larger second and third order nonlinear propertiesthan presently used inorganic electrooptic materials.

It is desired to provide a NLO molecule with ends having both donorswith an acceptor being in the middle. It is further desired to tie bothends of a NLO active molecule into a polymer chain to provide enhancedstability over other NLO molecules in which only one end is tied to thepolymer backbone.

There are two main problems which are associated with polymericnonlinear optical materials. The first problem is dilution of the NLOeffect of a polymer. Dilution of the NLO effect occurs, for example,when a molecule possessing nonlinear optical coefficients is added to ahost material having only linear optical properties. As an illustration,it has been shown, in U.S. patent application Ser. No. 441,783, filed ofeven date herewith by J. J. Kester, that materials like diaminodiphenylsulphone (DADS) and oxydianiline (ODA) exhibit a nonlinear opticsusceptibility. When the nonlinear optical molecules, such as DADS orODA, are incorporated into a crosslinked structure of an epoxy polymer,films with second and third harmonic generating capabilities areproduced. However, the concentration of NLO molecules in thesecrosslinked polymers may be diluted by the presence of an epoxy resinwhich has very low NLO susceptibilities relative to the DADS and ODA.

The second problem associated with polymeric nonlinear optical materialsis relaxation of orientation of NLO groups within an oriented polymerdue to thermal processes.

The relaxation of the NLO effect has been documented in the literature,for example, in the aforementioned reference H. Hampsch et al.,Macromolecules 21, p. 528-530. These relaxation can occur at roomtemperature and be well below the glass transition, Tg, of the polymer.

Monomers having glycidyl groups such as tetraglycidylsulfonyldianiline,are disclosed in the reference, W. T. Hodges et al., "Evaluation ofExperimental Epoxy Monomers", SAMPE Quarterly, Volume 17, No. 1, October1985, pp 21-25.

It would be highly desirable to provide an epoxy monomer havingnonlinear properties and to provide epoxy based polymeric nonlinearoptical materials with improved NLO properties and improved relaxationproperties.

An object of the present invention is to provide an epoxy based polymerswhich exhibit nonlinear optical effects and which have enhancedstability of nonlinear optical effects.

SUMMARY OF THE INVENTION

One broad aspect of the present invention is a non-linear opticalmaterial comprising an epoxy-containing polymeric material compositionhaving non-linear optical properties. For example, the epoxy-containingpolymeric material of the present invention contains glycidyl groups.

Another aspect of the present invention is a non-linear opticalcomposition characterized by the following formulae: ##STR1## where A isa divalent electron-withdrawing group: n is 2 or 3; each R isindependently a hydrogen, an epoxy-containing group or an aliphatic oraromatic hydrocarbon having from 1 to about 12 carbon atoms, with theproviso that at least two R groups on different nitrogen groups ##STR2##must be epoxy-containing groups; and X is a divalent or trivalentorganic hydrocarbon, hetero-interrupted hydrocarbon, or substitutedhydrocarbon radical or ##STR3##

Another broad aspect of the invention is a process for making anonlinear optical composition of the above formulae.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In accordance with the present invention, it has been discovered thatthe relaxation properties of NLO polymers follow the same sequentialorder as the glass transition (T_(g)) of the polymers. Therefore, toimprove the stability of these NLO polymers, the T_(g) of the polymersshould be increased. The glass transition of, for example, diaminodiphenylsulphone (DADS) cured polymers is typically between 200°-220° C.when using, for example, a bifunctional bisphenol A type epoxy resin.Accordingly, in the present invention, the use of a multi-functionalepoxy resin with NLO capabilities would provide improvements overdilution of the NLO crosslink and thermal relaxation properties.

In its broadest scope, the composition of the present invention includesa nonlinear optical material comprising an epoxy-containing polymericmaterial having nonlinear optical susceptibility. By "epoxy-containinggroup" herein means a group containing an epoxide group ##STR4##

Epoxy-containing groups useful in this invention include a wide varietyof epoxy-containing groups. The epoxy group may be internally,terminally, or in cyclic structures. The epoxy-containing group can befor example a glycidyl group ##STR5## formed from the reaction of anepihalohydrin such as epichlorohydrin. The epoxy-containing group canalso be formed from oxidation of olefin containing chains orcycloaliphatic dienes such as: ##STR6##

Generally, the nonlinear optical material comprises an epoxy-containingcomposition exhibiting non-linear optical properties containing permolecule (a) at least two epoxy-containing groups attached to more thanone of the nitrogen atoms which is attached to an aromatic ring and (b)at least one divalent electron-withdrawing group attached to an aromaticring.

Because of the presence of a charge asymmetry in the polymer of thepresent invention, the present invention polymer with anoncentrosymmetric molecular configuration advantageously exhibitssecond order nonlinear optical susceptibility.

One embodiment of the present invention is a nonlinear optical materialcomprising an epoxy-containing polymeric material composition havingnonlinear optical properties and characterized by the following formula:##STR7## wherein A is an electron-withdrawing molecule and each R isindependently a hydrogen, an epoxy-containing group, or an aliphatic oraromatic hydrocarbon having from 1 to about 12 carbon atoms, with theproviso that at least two R groups must be glycidyl groups on differentnitrogen groups; said composition exhibiting nonlinear properties.

Another embodiment of the present invention is a nonlinear opticalmaterial comprising an epoxy-containing polymeric material compositionhaving nonlinear optical properties and characterized by the followingformula: ##STR8## where A is a divalent electron-withdrawing group; n is2 or 3; each R is independently a hydrogen, an epoxy-containing group oran aliphatic or aromatic hydrocarbon having from 1 to about 12 carbonatoms with the proviso that at least two R groups must beepoxy-containing groups on different nitrogen groups: and X is adivalent or trivalent organic hydrocarbon, hetero-interruptedhydrocarbon, or substituted hydrocarbon radical or ##STR9##

The epoxy-containing groups are preferably glycidyl groups. Thus, oneembodiment of the Formula I above of a nonlinear optical composition ofthe present invention having glycidyl groups may be generally describedby the following general formula: ##STR10## where A is a divalentelectron-withdrawing group and and each R' is independently a hydrogenor a alkyl group containing from 1 to about 4 carbon atoms.

The electron-withdrawing group A of the above formulae is chemicallybonded between two substituents of the resultant product composition.The term "electron-withdrawing" as employed herein refers to organicsubstituents which attract n-electrons from a conjugated electronicstructure. Illustrative of electron-withdrawing substituents asrepresented by A in the above formula may be, for example, ##STR11##

The term "conjugating" group as employed herein refers to a group whichhas the ability to transfer charge from the electron-donating group tothe electron withdrawing group through a conjugated system of doublebonds. Conjugating groups include groups which have, for example, ahydrocarbyl diradical composed of aromatic rings optionally linked bycarbon-carbon, carbon-nitrogen, or nitrogen-nitrogen double bonds. Thisconjugating group may be substituted with pendant radicals such asalkyl, aryl, cyano, halo, and nitro.

The term "electron-donating" group as employed herein refers to organicsubstituents which contribute n-electrons to a conjugated electronicstructure. An electron donating group can be, for example, --NH₂.

Another more preferred embodiment of the Formula I above of a non-linearoptical composition of the present invention is atetraglycidylsulfonyldianiline (TGDDS) which can be described by thefollowing general formula: ##STR12## Both the 3,3' and 4,4'-isomers ofTGDDS are suitably used herein.

Another more preferred embodiment of the Formula I above of a non-linearoptical composition of the present invention is atetraglycidylcarbonyldianiline (TGCDA) which can be described by thefollowing general formula: ##STR13##

The epoxy monomers and oligomers of the present invention havingglycidyl groups may be prepared by known methods such as described inU.S. Pat. Nos. 4,814,414 and 4,521,583 and W. T. Hodges et al.,"Evaluation of Experimental Epoxy Monomers", SAMPE Quarterly, Volume 17,No. 1, October 1982, pp 21-25 , all (incorporated herein by reference.)

In carrying out the process of the present invention, the glycidyl amineepoxy-containing compounds of the present invention is prepared byreaction of the parent amine compound with a halohydrin including, butnot limited to, epichlorohydrin or epibromohydrin followed by furtherreaction with a basic material such as aqueous sodium hydroxide. Thereaction is carried out at elevated temperature (50°-60° C.) and atatmospheric pressure. A catalyst may be used to facilitate reactionbetween the parent amine and the halohydrin, such as benzyltrimethylammonium chloride, however, it is not essential that a catalyst bepresent for reaction to occur.

The present invention also provides a reaction product compositionresulting from reacting, as a first component (A) at least oneepoxy-containing compound exhibiting non-linear optical propertiescontaining per molecule (a) at least two epoxy-containing groupsattached to more than one nitrogen atoms which is attached to anaromatic ring and (b) at least one divalent electron-withdrawing groupattached to an aromatic ring with, as a second component (B) at leastone curing agent for component (A).

Component (A) is any of the glycidyl amine epoxy compounds describedabove with reference to Formulae I and II.

The second component (B) of the present invention is a curing agent forcomponent (A).

Component (B) of the present invention may comprise substantially all ofone curing agent compound or component (B) may be a mixture of two ormore curing agent compounds. The curing agent compound suitably usedherein may be a compound which does not exhibit a NLO response, acompound which does exhibit a NLO response or a combination thereof. Forexample, curing agent compounds which exhibit a NLO response and whichmay be used in the present invention may be those compounds described inU.S. patent application Ser. No. 441,783, filed of even date herewith,by J. J. Kester, incorporated herein by reference. An example of acuring agent disclosed in U.S. Ser. No. 441,783 which exhibits a NLOresponse and may be suitably used herein is diaminodiphenylsulfone.

Other curing agents which exhibit a NLO response and which can be usedherein are disclosed in U.S. application No. 441,731, filed of even dateherewith, by J. J. Kester; incorporated herein by reference. An exampleof a curing agent disclosed in U.S. Ser. No. 441,731 which exhibits aNLO response and may be suitably used herein is paranitroaniline.

Examples of other curing agents which can be used in the presentinvention include, for example, the amines disclosed in U.S. Pat. Nos.4,659,177; 4,707,303 and 4,707,305 which are hereby incorporated byreference, such as quinodimethane compounds, diphenoquinodimethanecompounds and naphthoquinodimethane compounds.

Other suitable curing agent compounds which can be employed herein ascomponent (B) include, for example, amines, acids or anhydrides thereof,biguanides, imidazoles, urea aldehyde resins, melaminealdehyde resins,phenolics, halogenated phenolics, sulfides, combinations thereof and thelike. These and other curing agents are disclosed in Lee and Neville'sHandbook of Epoxy Resins, McGraw-Hill Book Co., 1967 which isincorporated herein by reference. Particularly suitable curing agentsinclude, for example, dicyandiamide, diaminodiphenylsulfone,2-methylimidazole, diethylenetoluenediamine, bisphenol A,tetrabromobisphenol A, phenolformaldehyde novolac resins, halogenatedphenolformaldehyde resins, hydrocarbonphenol resins, combinationsthereof and the like.

The amines suitably employed herein can be multifunctional aliphatic,such as, diethylene triamine or triethylenetetramine, or aromaticamines, such as, metaphenylene diamine or methylene dianiline. Somecommercial curing agents useful in the present invention include, forexample. D.E.H.™ 20 and D.E.H.™ 24 commercially available from The DowChemical Company.

Generally, the amounts of components (A) and (B) employed herein aresufficient to provide a cured product. Usually the amounts of components(A) and (B) which provide a ratio of equivalents of curing agent perepoxy groups of from about 0.5 to about 1.2; preferably from about 0.75to about 1.1 and more preferably from about 0.95 to about 1.05 are usedherein.

The present invention also provides a reaction product resulting fromreacting, as a first component (A) a mixture of (1) at least oneepoxy-containing compound exhibiting non-linear optical propertiescontaining per molecule (a) at least two epoxy-containing groupsattached to more than one nitrogen atoms which is attached to anaromatic ring and (b) at least one divalent electron-withdrawing groupattached to an aromatic ring and (2) at least one epoxy-containingcompound containing an average of more than one epoxide group permolecule: and, as a second component (B) at least one curing agent forcomponent (A).

The component (A)(1) used herein is any of the glycidyl amine epoxycompounds having nonlinear optical properties described above withreference to Formulae I and II.

In general, the level of addition of NLO moieties to polymer will be ashigh as possible to maximize the NLO effect. The level at addition willbe balanced by the stability and quality of the film desired to beproduced. The range of percentages for incorporated NLO moieties is fromabout 0.5 percent to about 100 percent. Component (A)(2) of the presentinvention includes a wide variety of epoxy-containing compounds.Generally, component (A)(2) is any epoxy compound having an average ofmore than one epoxide group per molecule. Preferably, the component(A)(2) is any compound having an average of more than one vicinalepoxide group per molecule. More preferably, the component (A)(2) may beany compound containing an average of more than one glycidyl group permolecule. Even more preferably, the component (A)(2) can be glycidylethers, glycidyl esters or glycidyl amines.

Illustrative of the preferred glycidyl ethers used in the presentinvention are the glycidyl ethers of polyhydric phenols including forexample, the glycidyl ethers of phenol or substituted phenol such as thealdehyde novolac resins particularly phenol-formaldehyde resins andcresol-formaldehyde resins. The glycidyl ethers of polyhydric phenolsalso may include the glycidyl ethers of bisphenols or substitutedbisphenols such as the glycidyl ether of bisphenol A. Other examples ofglycidyl ethers of polyhydric phenols useful in the present inventionare described in U.S. Pat. No. 4,330,659 incorporated herein byreference, for example diglycidyl ethers of bisphenols corresponding tothe formula: ##STR14## wherein m is from 0 to about 50 and X is --CH₂--, ##STR15## These represent, respectively, bisphenols F, A, S and AP.Other applicable ether include the diglycidyl ethers of resorcinol,catechol, hydroquinone, and the like. The various ethers may besubstituted on the respective phenyl rings by such non-reactivesubstituents as alkyl, halogen, and the like. The glycidyl ethers ofcompounds having more than one aromatic hydroxyl group per molecule aredisclosed in U.S. Pat. No. 4,829,133, incorporated herein by referencefor the teachings of these epoxy resins. The glycidyl ethers ofhydrocarbon-phenol resins disclosed in U.S. Pat. No. 4,710,429,incorporated herein by reference, may also be used in the presentinvention.

Component (A)(2) of the present invention also includes di- orpolyepoxides of aliphatic or cycloaliphatic compounds containing morethan one epoxidizable unsaturated group, for example, the diepoxides ofcyclohexadiene, butadiene and the like.

Component (A)(2) used herein can be any combination of theaforementioned epoxy-containing compounds. Therefore, another embodimentof the present invention is the use of a mixture or a blend ofepoxy-containing compounds. The epoxy compositions of component (A)(2)may contain the same or other moieties with electron-withdrawing groups.

The epoxy compound used herein as component (A)(2) may be an epoxycompound which does not exhibit a NLO response, an epoxy compound whichdoes exhibit a NLO response or a combination thereof. For example, anepoxy compound which exhibits an NLO response and which may be used inthe present invention may be any of the glycidyl amine epoxy-containingcompounds described herein with reference to Formulae I and II, forexample, such as tetraglycidylsulfonyldianiline.

Other epoxy-containing compounds suitably used herein as component(A)(2) can be a monomer, oligomer or polymer resin. Epoxy monomers andoligomer units suitably used herein as component (A)(2) are described inthe Encyclopedia of Chemical Technology, vol. 9, pp 267-290, publishedby John Wiley & Sons, 1980. Examples of the epoxy resins suitably usedherein include, for example, novolak epoxy resins such as cresol-novolakepoxy resins and epoxy phenol novolak resin; bisphenol-A epoxy resinssuch as diglycidyl ethers of bisphenol A; cycloalkyl epoxy resins;glycidyl amine resins; triazine resins; hydantoin epoxy resins andcombinations thereof.

Some commercial epoxy resins useful in the present invention ascomponent (A)(2) include, for example, D.E.R.™ 331, D.E.R.™ 332, D.E.R.™383, D.E.N.™ 431 and D.E.R.™736, all commercially available from The DowChemical Company.

A solvent may be used, if desired, to dissolve an epoxy compound usedherein for example when using certain solid epoxy resins. Suitablesolvents which can be employed herein include, for example, glycolethers, ketones, aromatic hydrocarbons, alcohols, amides, combinationsthereof and the like. Particularly suitable solvents employed hereininclude, for example, methyl ethyl ketone, acetone, methanol,dimethylformamide, ethylene glycol methyl ether, propylene glycol methylether, combinations thereof and the like.

The present invention also provides a nonlinear optical materialcomposition comprising the reaction product of aforementioned component(A) at least one epoxy-containing composition exhibiting non-linearoptical properties containing per molecule (a) at least twoepoxy-containing groups attached to more than one nitrogen atoms whichis attached to an aromatic ring attached to an aromatic ring and at (b)least one divalent electron-withdrawing group attached to an aromaticring; and as a second component, herein referred to as component (C), atleast one compound containing an average of about two aromatic hydroxylgroups per molecule; wherein said resultant reaction product containsepoxy groups and said reaction product exhibits nonlinear opticalproperties. A reaction product of component (C) with components (A)(1)and (A)(2) described above is also included in the present invention.

Advanced resins of the nonlinear optical material of the presentinvention are prepared by reacting component (A) with component (C) acompound containing an average of about two aromatic hydroxyl groups permolecule. The aromatic hydroxyl-containing compounds (component (C)) andtheir formulas are disclosed in U.S. Patent Nos. 3,447,990; 3,948,955and 4,829,133, all incorporated herein by reference for their teachingsof the aromatic hydroxyl-containing compounds.

Any of the compositions of the present invention advantageously exhibita nonlinear optical response. Generally, the present invention includesa nonlinear optical material comprising an epoxy resin polymer based onthe compositions of the present invention having nonlinear opticalmoieties chemically bonded in the resultant polymer. In carrying out anyof the reaction processes of the present invention, for example whenreacting component (A), with component (B), the reaction conditions aresuch that a nonlinear optical composition of the present invention isformed.

To fully incorporate a curing agent having a strong electron-withdrawinggroup, a catalyst may be advantageously used in the present invention.It is possible to carry out the reaction with a catalyst present tofacilitate opening of the oxirane ring. For example, the catalyst can be2-methyl imidazole. Preferably, the reaction is carried out in thepresence of a catalyst because of the relative unreactivity of thearomatic amines of the first curing agent containingelectron-withdrawing substituents.

Catalysts which are suitably used here include, for example,tetrabutylphosphonium acetate, boron trifluoride monoethylamine,benzyldimethyl amine, and 2-methyl imidazole. The catalyst 2-methylimidazole is the most preferred because it tended to work withoutintroducing additional ionic species into the product material. Thereduction of ionic species in the polymer material is important for itsreduction of conductivity which can lead to a catastrophic breakdownduring the orientation process of the polymer product.

Suitable catalysts or promoters or accelerators which can be employed inthe preparation of the compositions of the present invention mayinclude, for example, tertiary amines, imidazoles, phosphoniumcompounds, ammonium compounds, sulfonium compounds, mixtures thereof andthe like.

Suitable tertiary amines include, for example, triethylenediamine,N-methylmorpholine, triethylamine, tributylamine, benzyldimethylamine,tris(dimethylaminomethyl)phenol, mixtures thereof and the like.

Suitable imidazoles include, for example, 2-methylimidazole,1-propylimidazole, mixtures thereof and the like.

Suitable phosphonium compounds include, for example, those disclosed byDante et al. in U.S. Pat. No. 3,477,990, Ferry in Canadian Pat. No.893,191 and U.S. Pat. No. 4,366,295 and by Tyler, Jr. et al. in U.S.Pat. No. 4,366,295 all of which are incorporated herein by reference.

Suitable quaternary ammonium compounds include, for example, benzyltrimethyl ammonium chloride, benzyl trimethyl ammonium hydroxide,tetrabutyl ammonium chloride, tetrabutyl ammonium hydroxide, mixturesthereof and the like.

Reaction mixtures used in the present invention may be characterized bydifferential scanning calorimetry (DSC), nuclear magnetic resonance(NMR), high pressure liquid chromatography (HPLC), ultraviolet-visible(UV-VIS) absorption and size exclusion chromatography.

The reaction conditions used in the present invention will varydepending on the particular reactants used. Generally, the reactants,for example components (A) and (B), are mixed together to form asolution and then heated to a temperature such that the components willreact. The reaction process of the present invention is preferablycarried out at a temperature of from about room temperature (about 20°C.) to about 300° C. and more preferably from about room temperature toabout 250° C. Above about 300° C. degradation of the epoxy polymer mayoccur and below about room temperature no reaction may occur.Optionally, the reactants are degassed to less than about 1×10⁻² Torr.The degassing is preferred to remove bubbles and moisture which may formin the reactants. The degassing is generally carried out a temperatureat which the reactants have a reduced viscosity. While the degassingtemperature depends on the reactants used, generally the degassingtemperature is below the temperature of sublimation of reactants orbelow the reaction temperature. The reaction process of the presentinvention is preferably carried out under an inert atmosphere such asnitrogen. The reaction mixture is heated under nitrogen to until asubstantially polymerized product is obtained. Generally, the period oftime for the reaction depends on the kinetics of the particularreactants, but preferably the reaction time is less than 5 hours andmore preferably less than 1 hour. The reacted mixture is then cooled toroom temperature for use.

As an illustration of another embodiment of the process of the presentinvention, a prepolymer is first prepared by reacting component (A) withless than 100 percent of a first curing agent and then reacting theprepolymer with a second curing agent.

The second curing agent compound may be used to substantially completelyreact a prepolymer which has been prepared by reacting less than 100percent of a first curing agent (an NLO moiety) with an epoxy resin. Itis possible to completely use the prepolymer by continuinghomopolymerization brought about by a catalyst. Preferably, theprepolymer is fully cured using a second curing agent such asmetaphenylinediamine, because the final product exhibits certainimproved properties obtained by using the second curing agent such asgreater stability and higher glass transition temperature. Theprepolymer is preferred because it provides a final product withimproved properties such as film quality, optical clarity and stability.A sufficient amount of the second curing agent is added to theprepolymer to substantially react all of the remaining epoxy groups.

The present invention provides a thermoset polymeric composition withgood thermal stability and resistance to chemical attack. It is alsoadvantageous to provide epoxy based polymers having NLO propertiesbecause epoxy based polymers per se have heretofore been shown to haveresistance to chemical attack. This property is provided by thecrosslinking of the polymeric chains during polymerization.

The polymeric material of the present invention generally contains aglass transition temperature of from about 90° C. to about 300° C.,preferably above about 140° C. and more preferably above about 160° C.

The present invention provides a composition with nonlinear opticalproperties with improved stability. The increased stability arises formthe incorporation of a moiety with electron-withdrawing groups into thebackbone of a polymer as opposed to blending a moiety withelectron-withdrawing groups with a polymer host.

The epoxy based thermoset compositions of the present invention can bein the form of sheets, films, fibers or other shaped articles byconventional techniques. Generally, films are used in testing,electrooptic devices and waveguide applications.

A film can be prepared, for example, by constraining a mixture ofcomponents (A) and (B) between two planar substrates and thenpolymerizing the mixture to form a thin film. The films used fortesting, electrooptic devices and waveguides should be thin films.Generally, the film has a thickness of from about 500 Angstroms to about500 microns. Preferably, the thickness of the film is from about 1micron to about 25 microns.

The reaction mixture of an epoxy resin with a curing agent (aromaticamines with electron-withdrawing groups), preferably with the additionof other curing agents is placed on a surface to make a film. The filmmay be produced in a number of ways. For many prepolymer mixtures withlow viscosity a substrate is required. The mixture may be spread overthe surface by compression with another substrate, dip, spray, or spincoating. Thermal processing of the mixture disposed on a substrate andthe ultimate thermal and mechanical properties of the resultant polymeris dependent on the type of epoxy resin and curing agent utilized. Thedegree of stability required will then determine the type of polymercomponents needed. The techniques for mixing and polymerizing aresimilar to those known in the state of the art. One aspect of thepolymerization which improves the mechanical properties of the film isthe schedule of temperature ramping of the mixture to its final curetemperature. By staging the cure at intermediate temperatures theoptimal network structure is obtained. Retaining the final curetemperature for a period of hours is often necessary for the mostcomplete polymerization possible. The long term chemical and mechanicalstability of the final polymer will be dependent on the network formed.

After the polymerization of the mixture, the resulting film is orientedto produce a film with anisotropic properties needed for second harmonicgeneration. Orientation of the film is provided by applying an externalfield to the film.

The term "external field" as employed herein refers to an electric,magnetic or mechanical stress field which is applied to a substrate ofmobile organic molecules to induce dipolar alignment of the moleculesparallel to the field.

For example, application of a DC electric field produces orientation bytorque due to the interaction of the applied field and the net moleculardipole movement. AC and magnetic fields also can effect alignment.Mechanical stress induced alignment includes a physical method such asstretching a thin film or a chemical method such as coating a liquidcrystalline surface with an aligning polymer such as nylon. Theorientation can be achieved by corona poling or parallel plate poling.For parallel plate poling the film must be near and parallel to twoelectrodes with a large potential difference while the polymer is nearto or above its glass transition. The electrodes can be associated withthe substrate used for the formation of the film. For example, thesubstrate can be coated with a layer of indium-tin-oxide. If there areionic impurities in the polymer mixture then the electrodes may beshielded with dielectric layer to prevent electrical breakdown. Toobtain free standing films after the orientation process, a releaselayer is often deposited on the substrate before the mixture placed ontoit. Other configurations involving air or vacuum gaps can also be used.The electric field continues to be applied until the temperature of thepolymer is reduced to room temperature. This allows for the relaxationof the polymer to its highest density with while still having the fieldapplied. This densification should improve any relaxation due tomobility of pendant side-chains within voids in the polymer.

Generally, in preparing NLO materials with second order susceptibility,X.sup.(2), the NLO functionalities in the polymer must have a netalignment for the polymer to exhibit NLO properties. Typically, anelectric field is applied to orient the moieties in the polymer fornonlinear optical effect. This type of orientation is referred to hereinas electric field poling, parallel plate poling, or poling. Otherconventional methods for the orientation of the NLO moieties can becarried out by corona poling or through stretching the polymer.

In electric field poling, the polymeric material is raised above itsglass transition temperature, T_(g), because in this state, largemolecular motion is enhanced, and the nonlinear optic moieties can givea net orientation. However, orientation of the polymer has been observedto occur below the Tg. An intense electric field is then applied to thepolymeric composition to align the nonlinear optic moieties. Electricfield strengths of between about 0.05 to about 1.5 megavolts percentimeter (MV/cm) can be applied. The film is then cooled to roomtemperature with the electric field still applied. The field is thenremoved, resulting in a system where the nonlinear optic moieties arealigned within the polymer matrix.

The orientation of the anisotropic units within the film can occurduring or after polymerization. One method of orientation includesapplying an electric field to a polymer film which has previously beenprepared and polymerized.

Another method of orientation of the polymer of the present inventionfor producing nonlinear optical materials, includes polymerizing thepolymer while the polymer is under an electric field such that thenonlinear optical moieties are aligned in the electric field beforecomplete polymerization of the polymer takes place. This method oforientation will allow less stress on the ultimate polymer chain than ifthe electric field is applied after the NLO moieties are incorporatedinto the backbone of the polymer.

Another method for preparing thin films for nonlinear opticalapplications includes annealing of the polymer while simultaneouslypoling the polymer which will allow relaxation of the polymer around theoriented molecule. This process for producing an epoxy nonlinear opticalpolymeric film comprises raising the temperature of an epoxy polymericfilm containing NLO moieties to above the glass transition temperatureof the polymer, poling the film to orient the NLO moieties, lowering thetemperature to below the glass transition temperature, and annealing fora period of time whereby a stable NLO polymeric film is obtained. Afterthe temperature of a polymer has been raised to above the Tg and thepolymer has been poled, the temperature is reduced from about 10° C. toabout 30° C. below the Tg and maintained at this lower temperature toallow for densification. This "annealing" step is carried out so as tocause a reduced free volume in the film and thus less room for NLOmoieties to randomly reorient themselves which can lead to a decrease inthe NLO signal. Thus, this annealing process during polymer orientationmay advantageously improve the stability of the polymer.

The nonlinear optical response of a polymer is determined by thesusceptibility of the polymer to polarization by an oscillatingelectromagnetic field. The most important polarization components of amedium in contact with an electric field are the first orderpolarization components, i.e., the linear polarization, the second orderpolarization, i.e., the first nonlinear polarization, and the thirdorder polarization, i.e., the second nonlinear polarization. On amacroscopic level this can be expressed as:

    P=X.sup.(1) E.sup.(ω1) +X.sup.(2) E.sup.(ω1) E.sup.(ω2) +X.sup.(3) E.sup.(ω1)(ω2)(ω3)

where

P is the total induced polarization

E is the electric field at the frequency (ω_(i)), and

X^(i) are the susceptibility tensors for the linear, and first andsecond order nonlinear component of the polarization.

Specific components of the susceptibility tensor can be related tomeasurable coefficients. For second harmonic generation the secondharmonic coefficient d_(ijk) is defined by:

    d.sub.ijk (-2ω; ω, ω)=(1/2) X.sub.ijk (-2ω; ω, ω)

Because of the degeneracy of two of the fields in second harmonicgeneration, the standard notation for writing this coefficient is d_(iu)(-2ω; ω, ω). For the specific case where polymer films are oriented withtheir anisotropic components normal to the film surface the coefficientd₃₃ can be determined as detailed in Applied Physics Letters vol. 49 (5)p. 248-250 (1986). From a knowledge of the susceptibilities themolecular polarizabilities can be calculated if the molecular dipolemoment, the number density of the nonlinear molecules, the internalelectric field, and correction factors for local field effects areknown. This calculation, also detailed in the above article, allows thedetermination of the first order hyperpolarizability, β, and the secondorder hyperpolarizability, Y. To achieve a significant second orderpolarization it is essential that the nonlinear medium exhibit secondorder susceptibility, X.sup.(2), be greater than 10⁻⁹ esu. To achieve asignificant third order polarization it is essential that the nonlinearmedium exhibit third order susceptibility, X.sup.(3), be greater than10⁻¹³ esu.

A number of optical tests can be used to evaluate the nonlinear opticalproperties of the poled polymer films of the present invention. Forexample, the second order susceptibility components of the polymer canbe tested by measuring the linear Pockels electro-optic effect, secondharmonic generation (SHG), or frequency mixing. For example, the thirdorder susceptibility components of the polymer can be measured by thirdharmonic generation (THG), nonlinear mixing, Kerr effect, degeneratefour wave mixing, intensity dependent refractive index, self-focusing,quadratic Kerr electro-optic effect, and electric field induce secondharmonic generation. Such optical tests and procedures are well known tothose skilled in the art.

The Maker fringe technique is a conventional procedure used herein todetermine the second order susceptibility properties of films. Inaccordance with this test procedure, the magnitude of the intensity ofthe light generated at the second harmonic of the incident frequency bythe polymeric film sample can be measured as a function of the incidentangle of the light irradiating the sample surface. If the film isoriented such that the anisotropic groups have a net orientation normalto the surface the largest second harmonic coefficient, d₃₃, can bedetermined using p-polarized incident radiation.

Typically a Q-switched Yd:YAG laser which emits electromagneticradiation at 1.064 microns, has a pulse half width of 14 ns, arepetition rate of 10 Hz, and is p-polarized, is focused onto a sampleon the rotation axis of a rotary stage. The light emitted from thesample is filtered to remove the incident frequency and a spike filtercentered near the second harmonic to allow passage of substantially onlythe second harmonic. Typically, the spike filter is centered at 530 nmand has a half width of 10 nm. The light is detected by aphotomultiplier and averaged by a boxcar which is triggered by theincoming laser pulse. The averaged output of the boxcar was collected bya computer as a function of the angle of incidence of the incident beamon the sample.

The second harmonic coefficient is calculated using the equationsdescribed in Applied Physics Letters volume 49, page 248-250 (1986) byK. Singer et al. The incident energy density on the sample is obtainedby calibration with a known quartz sample. A Y cut quartz slab is placedon the rotation stage in the same position as the polymer sample to betested. The energy density is calculated from the given equationsknowing the coefficient d₁₁ =1.1×10⁻⁹ esu. The intensity as a functionof incident angle for the polymer test sample is then fit by thecomputer with the additional information of incident energy density,film thickness, and indices of refraction at the incident and secondharmonic wavelength.

The polymers of the present invention have high stability (both thermaland chemical). An important feature of the NLO polymers derived fromepoxy resins of the present invention is an added stability of the NLOsignal of said polymers because the NLO groups are covalently bound intothe polymer chain. This improvement of the stability is related to thelevel of crosslinking of the polymer chain.

Enhanced stability may be determined by observing the decay of the NLOcapabilities as a function of time at room temperature. However, thisdetermination may be very time consuming. A more straight forwardapproach to determining stability is to observe the NLO signal at roomtemperature after exposure to elevated temperatures for periods of timenecessary to allow relaxation of the NLO effect. It has been found thatthe relaxation of the NLO effect is very rapid and the level isdependent on the temperature. The higher the temperature beforerelaxation of the NLO effect the more stable the polymer will be at roomtemperature. It is possible to calculate an activation energy for therelaxation of a particular NLO polymer. Another measure of the stabilityof a polymer's NLO effect is the ability to retain a certain percentageof its original NLO activity after exposure to an elevated temperature.One standard percentage would be 67.5 percent of the original value. Thedefinition of a "stable" NLO polymer herein means the ability to retaingreater than about 67.5 percent of its original NLO activity afterexposure to a specified temperature for 15 minutes.

Nonlinear optical materials have many potential applications usingharmonic generation for shifting laser light to shorter wavelengths,parametric oscillation for shifting laser light to longer wavelengths,phase conjugation (four-wave mixing), and sum frequency generation forapplications such as modulation and switching of light signals,imagining/processing/correlation, optical communications, opticalcomputing, holographic optical memories, and spatial light modulators.

The films of the present invention are particularly useful in theelectronic and communications fields to alter incident electromagneticwaves by the optical properties of the films. More particularly, thefilms of the present invention are used for waveguides and electroopticmodulators.

In another embodiment of this invention, there is provided anelectrooptic light modulator or optical parametric device with a(noncrystalline second order) polymeric nonlinear optical component anda means for providing an optical input to and output from saidcomponent. The component comprises an optically transparent medium of apolymer characterized by the compositions of the present invention. Whenthe device is employed in an electrooptic mode it includes means forapplying an electric field and/or optical input to said element foraltering an optical property.

One problem in obtaining an optically nonlinear medium for deviceapplications is the difficulty in providing stable uniform crystallinestructures and thin films of such materials in a manner suitable forintegrated devices. A media has been developed which is used inelectrooptic and optical parametric devices which provide improvedstability by means of incorporation of NLO active functionalities intothe backbone of noncrystalline epoxy based polymers.

The basis for any nonlinear optical device is the nonlinear opticalmedium therein. It has been found that to obtain a long lived polymericmedia comprising an oriented second order nonlinear material that theNLO active component must be bound into the polymer chain to provide thestabilization to thermal forces which would randomize the orientation.Such a nonlinear optical media can be prepared directly on a desiredsubstrate or can be a free standing film or tape. It may be noted thatthis optically nonlinear media can be utilized as an optical waveguideincorporated into electrooptic devices.

Media which can be used in electrooptic devices are described in thefollowing examples. The films suitable for use in electrooptic devicesmay be either free standing or on substrates. The substrates may berigid as in the case of glass, quartz, aluminum, silicon wafer, orindium-tin-oxide coated glass. For use in waveguide devices the NLOmedia must be adjacent to another media suitable for waveguidingconditions, for example, other polymeric materials with a lower index ofrefraction, such as, fluorinated hydrocarbon materials, or quartz orglass substrates. Electrodes of conductive material with a higher indexof refraction may be coated with polymeric materials of lower index toallow electrooptic modulation.

The following examples are for illustrative purposes only and are not tobe construed as limiting the scope of the invention in any manner.

EXAMPLE 1 A. Preparation of Epoxy Resin

An epoxy resin based on diamino diphenylsulfone (DAOS) molecule wasproduced according to the procedure disclosed in SAMPE Quarterly,October 1985, page 21 as follows:

30.0 g of DAOS (Aldrich), 7 ml HOAC, and 120 ml epichlorohydrin(Aldrich) were heated for about 30 hours at 50° C. and then cooled.Excess epichlorohydrin and HOAC were stripped off and the residue takeninto 100 ml MEK. The solution was taken to reflux and 80 g of 50%aqueous NaOH was added over a 2 hour period in 20 g aliquots. Thesolution was cooled and the organic layer was separated, washed withwater two times, and then dried with MgSO₄ and stripped to form ayellow/orange oil. The oil was titrated using the pyridine-HCl method.The epoxide equivalent weight (EEW) equaled 156 g (theoretical=118). Theproduct was characterized by proton NMR.

B. Preparation of Nonlinear Optical Polymer Films

A polymer film was produced by mixing 2.695 g of the tetraglycidyl amineof diamino diphenyl sulfone (DAOS-TGA) synthesized in Part A of thisexample with 1.10 g of DADS in a 100 ml boiling flask. This mixture washeated to 140° C. under a reduced pressure of at least 10⁻² Torr todissolve the DADS into the epoxy resin. The mixture was reduced to nearroom temperature and a small amount was placed between two quartz slideseach one having a thickness of 125 microns. In addition, a 25 micronpolyimide space layer was placed between the quartz slides to retain aconstant thickness. This combination of epoxy resin and curing agentsandwiched between two quartz slides was placed between two parallelelectrodes and the entire assembly was placed in an oven. Thetemperature was slowly raised to 240° C. at which time a voltage of 6000volts was applied across the electrodes to produce about a 200,000 v/cmelectric field. The temperature and field were retained on the samplefor about 2 hours. The temperature of the sample was then reduced toroom temperature over a period of about 6 hours. The field was left inplace during this time and at room temperature for a period of about 12hours. Differential scanning calorimetry on similarly prepared samplesindicated no glass transitions below the start of polymer degradationnear 280° C.

C. Measurement of the Nonlinear Optical Properties

The oriented polymer was removed from the electrode fixture and affixedto a stainless steel holder to allow reproducible positioning of thesample on the rotation stage for testing of the second harmoniccapabilities using a Maker fringe technique. The sample was illuminatedby a 1.064 micron wavelength laser beam having a 14 ns half width and a10 Hz repetition rate. The beam was focused onto the sample which wasmounted on the center of rotation of a rotary stage. The light emittedfrom the sample was filtered to remove the incident frequency and aspike filter centered at 530 nm and having a half width of 10 nm toallow passage of substantially only second harmonic light generated within the sample. The light was detected by a photomultiplier and averagedby a boxcar which was triggered by the incoming laser pulse. Theaveraged output of the boxcar was collected as a function of the angleof incidence of the incident beam on the sample. The second harmoniccoefficient was calculated using the equations described in AppliedPhysics Letters volume 49, page 248-250 (1986) by K. Singer et al. Thiscalculation requires the film thickness, the index of refraction at1.064 microns which was about 1.63 and the index at 532 nm which wasabout 1.60, and the energy density of the incident laser beam. Theincident energy density was calculated by using a Y cut quartz crystalhaving a d₁₁ =1.1×10⁻⁹ esu. The quartz sample was placed in the sameposition as the polymer sample immediately before testing. Knowing thesecond harmonic coefficient and indices of refraction of quartz theincident energy density can be calculated. Using these values the secondharmonic coefficient was estimated to be about 1×10⁻⁹ esu.

D. Thermal Stability Measurements of Nonlinear Optical Film

The stability of the film was measured by its ability to retain NLOactivity after exposure to elevated temperatures. The film describedabove was placed in an oven for a period of 30 minutes at an elevatedtemperature and then removed and tested as described in Part C above forsecond harmonic capability after the sample had returned to roomtemperature. The results of this testing are given in Table 1.

                  TABLE 1                                                         ______________________________________                                                       Second Harmonic                                                Temperature (°C.)                                                                     Coefficient (% relative)                                       ______________________________________                                         22            100                                                             50            100                                                             75            98                                                             100            100                                                            125            95                                                             150            91                                                             175            74                                                             200            57                                                             225            33                                                             ______________________________________                                    

This table shows that the DADS-TGA polymer cured with DADS is stable to175° C., i.e., it retained greater than 67 percent of its originalsecond harmonic coefficient after exposure to a temperature of 175° C.The values of this table have an estimated error of about plus or minus5 percent.

EXAMPLE 2

The 3.276 g of the epoxy resin produced in Example 1, DADS-TGA, wascombined with 0.520 g of triethylene tetramine having an amineequivalent weight of 24. This mixture was dissolved in 20 ml ofmethylene chloride. A quartz slide having a thickness of about 125microns was attached to a translation stage and was dipped into andpulled out of this solution at a constant rate of about 2 mm/sec. Theresin and curing agent was removed from one side of the quartz slide bysolvent washing. The samples were heated in a clean room oven at 100° C.for 30 minutes and 160° C. for one hour. This sample was further driedin a vacuum oven having a pressure of about 10⁻³ Torr at a temperatureof about 100° C. The polymer coated quartz slides were oriented byplacing the slide between two electrodes. A 12.5 micron spacer wasplaced adjacent to the polymer side of the quartz slide to preventdirect contact of the electrode with the polymer surface. The sample wasthen heated to 175° C. with an electric field strength of about 500,000V/cm. The sample was cooled slowly to room temperature with the fieldapplied. The glass transition of a polymer sample prepared from thereactant solution was very broad with a mid-point of the transitioncentered near 150° C.

The second harmonic coefficient of this sample was measured using thesame Maker fringe technique described in Example 1. The film thicknessof this film was measured to be about 0.88 microns. The second harmoniccoefficient, d₃₃, was calculated to be about 6×10⁻⁹ esu.

What is claimed is:
 1. A process for producing a non-linear opticalmaterial comprising applying an external field to an epoxy-containingcomposition exhibiting non-linear optical properties, represented by theformula: ##STR16## or ##STR17## where A is a divalentelectron-withdrawing group; n is 2 or 3; each R is independently anepoxy-containing group or an aliphatic or aromatic hydrocarbon havingfrom 1 to about 12 carbon atoms with the proviso that at least two Rgroups each on different nitrogen atoms must be epoxy-containing groups;and X is a divalent or trivalent unsubstituted organic hydrocarbon,hetero-interrupted hydrocarbon, or substituted hydrocarbon radical or##STR18##
 2. A process for producing a non-linear optical materialcomprising applying an external field to the reaction product obtainedby reaction of (A) and (B) wherein (A) is at least one epoxy-containingcomposition exhibiting non-linear optical properties, represented by theformula: ##STR19## or ##STR20## where A is a divalentelectron-withdrawing group; n is 2 or 3; each R is independently anepoxy-containing group or an aliphatic or aromatic hydrocarbon havingfrom 1 to about 12 carbon atoms with the proviso that at least two Rgroups each on different nitrogen atoms must be epoxy-containing groups;and X is a divalent or trivalent unsubstituted organic hydrocarbon,hetero-interrupted hydrocarbon, or substituted hydrocarbon radical or##STR21## (B) is at least one curing agent for component (A); wherebythe field applied to the reaction product is sufficient to induce a netorientation in the product.
 3. The process of claim 2 wherein component(A) is a mixture of (1), represented by the formula: ##STR22## or##STR23## where A is a divalent electron-withdrawing group; n is 2 or 3;each R is independently an epoxy-containing group or an aliphatic oraromatic hydrocarbon having from 1 to about 12 carbon atoms with theproviso that at least two R groups each on different nitrogen atoms mustbe epoxy-containing groups; and X is a divalent or trivalentunsubstituted organic hydrocarbon, hetero-interrupted hydrocarbon, orsubstituted hydrocarbon radical or ##STR24## and (2) at least oneepoxy-containing compound containing an average of more than one epoxidegroup per molecule which is other than (1).
 4. The process of claim 2wherein the field is applied by electric field poling.
 5. A process forpreparing a non-linear optical material comprising substantiallysimultaneously (i) polymerizing a mixture of (A) and (B) wherein (A) isat least one epoxy-containing composition exhibiting non-linear opticalproperties, represented by the formula: ##STR25## or ##STR26## where Ais a divalent electron-withdrawing group; n is 2 or 3; each R isindependently an epoxy-containing group or an aliphatic or aromatichydrocarbon having from 1 to about 12 carbon atoms with the proviso thatat least two R groups each on different nitrogen atoms must beepoxy-containing groups; and X is a divalent or trivalent unsubstitutedorganic hydrocarbon, hetero-interrupted hydrocarbon, or substitutedhydrocarbon radical or ##STR27## and (B) is at least one curing agentfor component (A);and (ii) applying an electric field to the mixture toform a material having non-linear optical properties.
 6. A process forpreparing a non-linear optical material comprising substantiallysimultaneously (i) applying an electric field to the reaction product of(A) and (B) wherein (A) is at lest one epoxy-containing compositionexhibiting non-linear optical properties, represented by the formula:##STR28## or ##STR29## where A is a divalent electron-withdrawing group;n is 2 or 3; each R is independently an epoxy-containing group or analiphatic or aromatic hydrocarbon having from 1 to about 12 carbon atomswith the proviso that at least two R groups each on different nitrogenatoms must be epoxy-containing groups; and X is a divalent or trivalentunsubstituted organic hydrocarbon, hetero-interrupted hydrocarbon, orsubstituted hydrocarbon radical or ##STR30## and (B) is at least onecuring agent for component (A);and (ii) thermally annealing the reactionproduct for a period of time sufficient to form a material havingnon-linear optical properties.